I was also VCP5-DCV (Forget about it), but still not VCP6-DCV
Not required.....U can go for forward to submit your design, as you are already have VCIX-6-DCV badge.
VCP6-DCV is not mandatory indeed.
It has been confirmed by certification support:
As per our conversation, please be informed VCP6-DCV Certificate is not mandatory for the VCDX6-DCV Certification, VCIX6-DCV badge will serve as a requirement.